The coking behavior of coal tar atmospheric residue (CTAR) during slurry-bed hydrocracking was studied. The CTAR hydrocracking was performed in the autoclave at 430 degrees C with H-2 pressure of 13 MPa, comparing with that of the Merey atmospheric residue (MRAR). The properties of C-7-asphaltene and toluene-insoluble in feedstocks and products were analyzed respectively to describe the CTAR coking behavior during slurry-bed hydrocracking. The experimental results showed that CTAR with higher asphaltene content (30 wt%) produced less amount of coke than MRAR with asphaltene content (9.29 wt%), and little coke on the inner surface of reactor was found. The toluene-insoluble in the feedstock contained the larger carbonaceous particles (about 7 mu m) and the inorganic fine particles (about 1 mu m). Both sulfurized catalyst particles and inorganic fine particles in CTAR provided independent condensation nuclear or growth nuclear for macromolecular radicals during slurry-bed hydrocracking. These particles promoted the dispersion of spherical coke precursor and inhibited the coalescence of coke precursor. The larger carbonaceous particles in CTAR carried spherical coke particles as coke-carrier.